GNU social Coding Style

Please comply with PSR-12 and the following standard when working on GNU social if you want your patches accepted and modules included in supported releases.

If you see code which doesn't comply with the below, please fix it :)

Programming Paradigms

GNU social is written with multiple programming paradigms in different places.

Most of GNU social code is procedural programming contained in functions whose name starts with on. Starting with "on" is making use of the Event dispatcher (onEventName). This allows for a declarative structure.

Hence, the most common function structure is the one in the following example:

public function onRainStart(array &$args): bool
    return true;

Things to note in the example above:

  • This function will be called when the event "RainStart" is dispatched, thus its declarative nature. More on that in the Events chapter.
  • We call a static function from a Util class. That's often how we use classes in GNU social. A notable exception being Entities. More on that in the Database chapter.

It's also common to have functional code snippets in the middle of otherwise entirely imperative blocks (e.g., for handling list manipulation). For this we often use the library Functional PHP.

Use of reflective programming, variable functions, and magic methods are sometimes employed in the core. These principles defy what is then adopted and recommended out of the core (components, plugins, etc.). The core is a lower level part of GNU social that carefully takes advantage of these resources. Unless contributing to the core, you most likely shouldn't use these.

PHP allows for a high level of code expression. In GNU social we have conventions for when each programming style should be adopted as well as methods for handling some common operations. Such an example is string parsing: We never chain various substring calls. We write a regex pattern and then call preg_match instead. All of this consistency highly contributes for a more readable and easier of maintaining code.


Use ' instead of " for strings, where substitutions aren't required. This is a performance issue, and prevents a lot of inconsistent coding styles. When using substitutions, use curly braces around your variables - like so:

$var = "my_var: {$my_var}";

Comments and Documentation

Comments go on the line ABOVE the code, NOT to the right of the code, unless it is very short. All functions and methods are to be documented using PhpDocumentor -

File Headers

File headers follow a consistent format, as such:

 // This file is part of GNU social -
 // GNU social is free software: you can redistribute it and/or modify
 // it under the terms of the GNU Affero General Public License as published by
 // the Free Software Foundation, either version 3 of the License, or
 // (at your option) any later version.
 // GNU social is distributed in the hope that it will be useful,
 // but WITHOUT ANY WARRANTY; without even the implied warranty of
 // GNU Affero General Public License for more details.
 // You should have received a copy of the GNU Affero General Public License
 // along with GNU social.  If not, see <>.

  * Description of this file.
  * @package   samples
  * @author    Diogo Cordeiro <>
  * @copyright 2019 Free Software Foundation, Inc
  * @license GNU AGPL v3 or later

Please use it.

A few notes:

  • The description of the file doesn't have to be exhaustive. Rather it's meant to be a short summary of what's in this file and what it does. Try to keep it to 1-5 lines. You can get more in-depth when documenting individual functions!

  • You'll probably see files with multiple authors, this is by design - many people contributed to GNU social or its forebears! If you are modifying an existing file, APPEND your own author line, and update the copyright year if needed. Do not replace existing ones.

Paragraph spacing

Where-ever possible, try to keep the lines to 80 characters. Don't sacrifice readability for it though - if it makes more sense to have it in one longer line, and it's more easily read that way, that's fine.

With assignments, avoid breaking them down into multiple lines unless neccesary, except for enumerations and arrays.

'If' statements format

Use switch statements where many else if's are going to be used. Switch/case is faster.

 if ($var === 'example') {
     echo 'This is only an example';
 } else {
     echo 'This is not a test.  This is the real thing';

Do NOT make if statements like this:

 if ($var === 'example'){ echo 'An example'; }

OR this

 if ($var === 'example')
         echo "An {$var}";

Associative arrays

Always use [] instead of array(). Associative arrays must be written in the following manner:

 $array = [
     'var' => 'value',
     'var2' => 'value2'

Note that spaces are preferred around the '=>'.

A note about shorthands

Some short hands are evil:

  • Use the long format for <?php. Do NOT use <?.
  • Use the long format for <?php echo. Do NOT use <?=.

Naming conventions

Respect PSR-12 first.

  • Classes use PascalCase (e.g. MyClass).
  • Functions/Methods use camelCase (e.g. myFunction).
  • Variables use snake_case (e.g. my_variable).

A note on variable names, etc. It must be possible to understand what is meant without necessarily seeing it in context, because the code that calls something might not always make it clear.

So if you have something like:


Well I can easily tell what you're doing there because the names are straight- forward and clear.

Something like this:


Is much less clear.

Also, wherever possible, avoid ambiguous terms. For example, don't use text as a term for a variable. Call back to "contents" above.


Even though PSR-12 doesn't specifically specify rules for array formatting, it is in the spirit of it to have every array element on a new line like is done for function and class method arguments and condition expressions, if there is more than one element. In this case, even the last element should end on a comma, to ease later element addition.

 $foo = ['first' => 'unu'];
 $bar = [
     'first'  => 'once',
     'second' => 'twice',
     'third'  => 'thrice',


Always use symbol based comparison operators (&&, ||) instead of text based operators (and, or) in an "if" clause as they are evaluated in different order and at different speeds. This is will prevent any confusion or strange results.

Prefer using === instead of == when possible. Version 3 started with PHP 8, use strict typing whenever possible. Using strict comparisons takes good advantage of that.

Use English

All variables, classes, methods, functions and comments must be in English. Bad english is easier to work with than having to babelfish code to work out how it works.


Files should be in UTF-8 encoding with UNIX line endings.

No ending tag

Files should not end with an ending php tag "?>". Any whitespace after the closing tag is sent to the browser and cause errors, so don't include them.

Nesting Functions

Avoid, if at all possible. When not possible, document the living daylights out of why you're nesting it. It's not always avoidable, but PHP has a lot of obscure problems that come up with using nested functions.

If you must use a nested function, be sure to have robust error-handling. This is a must and submissions including nested functions that do not have robust error handling will be rejected and you'll be asked to add it.


Properly enforcing scope of functions is something many PHP programmers don't do, but should.

In general:

  • Variables unique to a class should be protected and use interfacing to change them. This allows for input validation and making sure we don't have injection, especially when something's exposed to the API, that any program can use, and not all of them are going to be be safe and trusted.

  • Variables not unique to a class should be validated prior to every call, which is why it's generally not a good idea to re-use stuff across classes unless there's significant performance gains to doing so.

  • Classes should protect functions that they do not want overriden, but they should avoid protecting the constructor and destructor and related helper functions as this prevents proper inheritance.


PHP is a soft-typed language, it falls to us developers to make sure that we are using the proper inputs. When possible, use explicit type casting. Where it isn't, you're going to have to make sure that you check all your inputs before you pass them.

All inputs should be cast as an explicit PHP type.

Not properly typecasting is a shooting offence. Soft types let programmers get away with a lot of lazy code, but lazy code is buggy code, and frankly, we don't want it in GNU social if it's going to be buggy.

Consistent exception handling

Consistency is key to good code to begin with, but it is especially important to be consistent with how we handle errors. GNU social has a variety of built- in exception classes. Use them, wherever it's possible and appropriate, and they will do the heavy lifting for you.

Additionally, ensure you clean up any and all records and variables that need cleanup in a function using try { } finally { } even if you do not plan on catching exceptions (why wouldn't you, though? That's silly.).

If you do not call an exception handler, you must, at a minimum, record errors to the log using Log::level(message).

Ensure all possible control flows of a function have exception handling and cleanup, where appropriate. Don't leave endpoints with unhandled exceptions. Try not to leave something in an error state if it's avoidable.


When programming in PHP it's common having to represent the absence of value. A variable that wasn't initialized yet or a function that could not produce a value. On the latter, one could be tempted to throw an exception in these scenarios, but not always that kind of failure fits the panic/exception/crash category.

On the discussion of whether to use === null vs is_null(), the literature online is diverse and divided. We conducted an internal poll and the winner was is_null().

Some facts to consider:

  1. null is both a data type, and a value;
  2. As noted in PHP's documentation, the constant null forces a variable to be of type null;
  3. A variable with null value returns false in an isset() test, despite that, assigning a variable to NULL is not the same as unsetting it. To actually test whether a variable is set or not requires adopting different strategies per context (
  4. The void return type doesn't return NULL, but if used as an expression, it evaluates to null.

Considering union types and what we use null to represent, we believe that our use of null is always akin to that of a Option type. Here's an example:

function sometimes_has_answer(): ?int
    return random_int(1, 100) < 50 ? 42 : null;

$answer = sometimes_has_answer();
if (!is_null($answer)) {
    echo "Hey, we've got an {$answer}!";
} else {
    echo 'Sorry, no value. Better luck next time!';

A non-void function, by definition, is expected to return a value. If it couldn't and didn't run on an exceptional scenario, then you should test in a different style from that of regular strict comparison. Hence, as you're testing whether a variable is of type null, then you should use is_null($var). Just as you normally would with an is_int($var) or is_countable($var).

About nullable types, we prefer that you use the shorthand ?T instead of the full form T|null as it suggests that you're considering the possibility of not having the value of a certain variable. This apparent intent is reinforced by the fact that NULL can not be a standalone type in PHP.